I have a modular oven that came with a preformed arch made out of what lloks like clay. I tried attaching the arch to the oven using te refrax but that did not hold and I have also tried the motar i am using to build my brick surround but that did not stick either.
does anyone have suggestions on what o use to attach the arch to the front of the oven?

Try using a wood form/support/brace (a couple of 2"x4"s at an angle) to hold the arch in place while the mortar between the arch and the oven chamber sets. I would put a 3/8" strip between the arch and oven, then pack a good 1"x3" band around that joint.

That said, the mortar shouldn't have to "hold" the two together. The arch (I have a mental picture of oven you have) should stand freely and tightly next to the oven. The mortar really is just sealing the two together.

Let me know if that works. Of course this wouldn't happen with a Forno Bravo oven. Just joking.
James

With the brickwork I did I found there was some difficulty forming a bond until I learned (I think here) to soak the bricks first. Mortar cures best (like concrete) when it stays wet for a while (although wet mixed mortar is not as strong as a relatively dry mix), plus a too dry mortar joint has no "grip". The trick I think is to have a mortar you can spread like thick frosting (describing the consistency, others say like peanut butter) and let the masonry you are bonding provide water supply for the curing. Perhaps you can briefly soak the two pieces, or if that's impractical wet them with a brush or a wet rag. Really douse them if you are unable to soak them. If you do drown them first keep them under water until they stop hissing.

That will also help. A dry refractory will suck the moisture out of your mortar, and it won't cure properly. You can end up with hairline fractures and even cracks that let out hot air and smoke.
Thanks for that.
James

You are exactly correct about wetting the bricks when using refractory mortar. For those who are familiar with laying ordinary brick, the water will be sucked out of refractory mortar and fire bricks about three times as fast as with Type S mortar and ordinary bricks: common, fancy facade, what have you.

If you can't soak the bricks, as with standing bricks being added to, one at a time, brush the brick already in position with lots of water, then soak the brick to be applied until it stops hissing.

Lay three bricks, then point the joints to seal. This is much, much sooner than with ordinary mortar and bricks. Carve off squeeze-out at about the same rate; otherwise you'll be hunting for the cold chisel and hammer.

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